Method and system to detect ophthalmic tissue structure and pathologies

BACKGROUND

0001Field of the Invention

0002An apparatus to determine a structure and pathology of an ophthalmic tissue described herein relates to imaging and image processing systems for ophthalmology. More particularly, the embodiments disclosed herein relate to the field of surgical procedures to treat retinal pathologies such as epiretinal membrane, macular holes, and macular pucker.

0003Description of Related Art

0004Epiretinal membrane (ERM) is a disease in which a layer of tissue grows on the interior surface of the retina. While there may be multiple causes for this pathology, it usually is a natural aging degeneration. As shown in <figref idref="DRAWINGS">FIG. 1</figref>, a retina <b>110</b> is composed of three main tissue layers: an internal limiting membrane (ILM) <b>111</b>, in contact with vitreous gel <b>145</b> in the vitreous cavity <b>140</b>, a nerve fiber layer (NFL) <b>112</b>, and the optically sensitive neural layer. Retinal pigment epithelial cells are located (RPE) under the retina <b>113</b>. Underlying the RPE layer is the choroid <b>115</b>, which is a tissue containing blood vessels to provide oxygen and metabolic support to the RPE cells. Separating the RPE layer <b>113</b> and the choroid <b>115</b> is Bruch's membrane, allowing exchange of nutrients from the choroid <b>115</b> into the metabolically active RPE cells and waste material from the latter into the former.

0005As a result of the growth of an epiretinal membrane, the retina may become contracted or wrinkled in the macula area. The retina may become elevated away from the RPE causing damage to retinal function. These deformations result in defects of image formation at the macula, and need to be removed using a vitrectomy surgical procedure.

0006Vitreomacular traction is another pathological condition of the retina. Excessive adhesion between the vitreous and the ILM may result in the retina being elevated away from the RYE. As vitreous gel <b>145</b> moves anteriorly or is contracted, it may tear away portions of the inner surface of the retina into the vitreous chamber.

0007During surgical procedures to treat the above and other retinal pathologies it is necessary for the surgeon to distinguish between healthy portions of the retina and affected portions. The determination needs to be made in real time, as the surgeon proceeds with the intervention. Furthermore, the determination should require little involvement by the surgeon. The surgeon's attention should be focused on the physical procedure rather than analyzing ancillary information.

0008State-of-the-art methods to distinguish different tissue types involve the use of fluorescence techniques with differentiated markers. In a fluorescent marker approach, fluorophores emitting different colors of light are combined with suitable carriers that attach to a specific tissue. As a laser or other excitation light scans certain areas, the illumination spot turns into a different color, indicating the type of tissue being illuminated.

0009Unfortunately, the fluorescence approach may not be used for the treatment of retinal pathologies as described above. Typical fluorescent markers such as indocyanine green (ICG), trypan blue, and other stains have been used to stain ILM, with negative results. ICG is toxic and needs to be administered in low doses, and trypan blue produces weak stains that are difficult to see. Furthermore, there are no stains specific to ERM, and particulate marking of the vitreous humor, ERM, and ILM (e.g. using triamcinolone) is non-specific.

0010Other commonly used techniques may include tissue selective staining and observation with white light. ICG, Trypan blue, and Membrane Blue, are examples of some of the stains that may be used. The disadvantages of tissue staining are similar to those of fluorescence techniques mentioned above: toxicity to tissue (especially to sub-retinal tissues such as choroid <b>115</b>) and the need to remove the dye after the procedure. Therefore, there is a need for a method and an apparatus to detect and determine tissue structure on an area to assess whether or not to perform a surgical procedure on that area. Also, a method is needed to detect tissue structure in real time without surgeon intervention to analyze data before making the determination.

SUMMARY

0011According to embodiments disclosed herein, a method to determine ophthalmic tissue structure comprises measuring image data for a range of depths corresponding to a target point in an eye with an axial scanner with a probe; determining an image information by an imaging processor from the image data; identifying a tissue pathology corresponding to the target point by the imaging processor from the image information; and signaling a user by a user indicator based on the identified tissue pathology.

0012According to embodiments disclosed herein, an apparatus to determine an ophthalmic tissue pathology comprises an axial scanner with a probe, configured to measure image data for a range of depths corresponding to a target point in an eye; an imaging processor, configured to determine an image information from the image data, and to identify a tissue pathology corresponding to the target point from the image information; and a user indicator configured to signal a user based on the identified tissue pathology.

0013These and other embodiments of the present invention will be described in further detail below with reference to the following drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

<figref idref="DRAWINGS">FIG. 1</figref> shows a schematic view of the human eye including the retina, the optic nerve, and the vitreous gel.

<figref idref="DRAWINGS">FIG. 2</figref> shows a schematic view of pathologies and corresponding retinal structures to be treated using a method according to some embodiments.

<figref idref="DRAWINGS">FIG. 3</figref> shows a flow chart of a method to detect tissue structure using an axial scanner with a probe, according to some embodiments.

<figref idref="DRAWINGS">FIG. 4</figref> shows a partial view of an OCT B-scan of a retina, according to some embodiments.

<figref idref="DRAWINGS">FIG. 5</figref> shows a partial view of a one-axis OCT A-scan of a healthy retina, according to some embodiments.

<figref idref="DRAWINGS">FIG. 6</figref> shows a system to detect tissue structure in ophthalmic surgery according to some embodiments.

0020In the figures, elements having the same reference number have the same or similar functions.

DETAILED DESCRIPTION

0021<figref idref="DRAWINGS">FIG. 1</figref> shows a schematic view of the human eye <b>100</b>, including retina <b>110</b>, optic nerve <b>150</b>, and vitreous gel <b>145</b>, as they are relevant for embodiments disclosed herein. Portions of eye <b>100</b> located in the front, such as the iris, the cornea, the sclera, the pupil, and the lens are also shown in <figref idref="DRAWINGS">FIG. 1</figref> for completeness. Vitreous gel <b>145</b> is the material filling vitreous cavity <b>140</b>, which is limited in the back portion by retina <b>110</b>. Macula <b>120</b> is a portion of retina <b>110</b> having a center at fovea <b>130</b>, where the central vision is collected. The lens creates an image that is centered on macula <b>120</b>. Retinal tissue layers such as ILM <b>111</b>, NFL <b>112</b>, and RPE <b>113</b>, are also illustrated in <figref idref="DRAWINGS">FIG. 1</figref> and have been described above.

0022The lens creates an image that is centered on fovea <b>130</b>, covering macula <b>120</b> and other parts of retina <b>110</b>. Optical rays traverse NFL <b>112</b> and reach RPE <b>113</b> where they excite photosensitive cells that generate stimulus pulses. The stimulus pulses from RPE <b>113</b> are transmitted by NFL <b>112</b> to optic nerve <b>150</b>, which in turn transmits the signal to the brain, where an image is created.

0023<figref idref="DRAWINGS">FIG. 2</figref> shows a schematic view of pathologies <b>201</b>-<b>205</b> with retinal structures <b>211</b>-<b>215</b> to be treated using a method according to some embodiments. A detailed description of each tissue structure <b>201</b>-<b>205</b> follows.

0024Rheghmatogenous retinal detachment <b>201</b> is a common form of ERM where a full-thickness portion <b>211</b> of retina <b>110</b> detaches and dangles into vitreous chamber <b>140</b>. A portion of vitreous gel <b>221</b> moves underneath detached retinal portion <b>211</b>.

0025Vitreous traction <b>202</b> has been described in the background section. In a traction event <b>202</b>, a portion of the retina <b>110</b> is pulled from its base by vitreous gel <b>145</b>, creating a cusp-like structure <b>212</b>. Underneath detached portion <b>212</b>, material <b>222</b> including vitreous gel, hemorrhagic blood and inflammatory cells moves into place.

0026Retinal detachment <b>203</b> may be provoked by hemorrhagic or exudative events where blood or fluid <b>223</b> builds up under retina <b>110</b>, creating a hump-like structure <b>213</b>. Macular puckering <b>204</b> occurs when cells in retina <b>110</b> become stressed, e.g. due to an immune system response. The tension generated due to convergence of immune cells on the tissue may cause retina <b>110</b> to pucker and form a wrinkled portion. <b>214</b>. A retinal pucker may occur anywhere in the retina, including macula <b>120</b>. Macular pucker is optimally referred to as epimacular membrane.

0027Posterior vitreous detachment (also known as vitreous cortex) <b>205</b> is the consequence of liquefaction of vitreous gel <b>145</b>. This process is typically the result of aging. Vitreous gel <b>145</b> may contract forming a cortex <b>215</b>, leaving behind liquid portions <b>216</b> that may need to be removed. The vitreous contraction and the liquid <b>216</b> may induce a small tear in retinal tissue, leading to a macular hole (see below).

0028Other retinal pathologies may be consistent in general with the five structures <b>211</b>-<b>215</b> shown in <figref idref="DRAWINGS">FIG. 2</figref>. Embodiments of the methods, procedures, and apparatus disclosed herein are not limited to the pathologies depicted in <figref idref="DRAWINGS">FIG. 2</figref>, as other pathologies may be well known to those skilled in the art of ophthalmic surgery.

0029Some embodiments of the methods, procedures and apparatus disclosed herein may be used in surgical tasks such as finding retinal rupture points and other disruptions, or as a general surgical tool to e.g. locate retina-attached vitreous gel that may remain in the retina after an extraction procedure.

0030Some embodiments of the methods, procedures and apparatus disclosed herein may be used in the treatment of sub-retinal pathologies, e.g. pathologies affecting the choroid <b>115</b> and sclera. Another retinal pathology that may be treated using methods, procedures and an apparatus consistent with this disclosure may be macular hole. Macular hole is the result of vitreous traction in macula <b>120</b>.

0031When a surgeon intervenes in a patient for any of the pathologies depicted in <figref idref="DRAWINGS">FIG. 2</figref>, precise knowledge of the nature of the structure at the point of intervention is desirable. As the intervention proceeds, information about the underlying structure needs to be updated without hindering the progress of the procedure.

0032<figref idref="DRAWINGS">FIG. 3</figref> shows a flow chart of method <b>300</b> to determine an ophthalmic tissue structure, the method comprising the following steps. Step <b>310</b> can involve measuring image data for a range of depths corresponding to a target point in an eye with an axial scanner with a probe. Step <b>320</b> can involve determining an image information by the imaging processor from the image data. In step <b>330</b>, identifying a tissue pathology, structure, or anomaly corresponding to the target point by the imaging processor from the image information can be performed. Finally, step <b>340</b> can involve signaling a user by a user indicator based on the identified tissue pathology. These steps will now be described in detail.

0033In step <b>310</b>, image data can be measured by an Optical Coherence Tomography (OCT) imaging system or by any other type of axial scanner. OCT imaging systems and axial scanners are configured to gather imaging data corresponding to a target point for a range of depths. Correspondingly, an OCT or an axial scanner imaging system can image the target tissue over the range of depth.

0034An OCT imaging system can include a laser source to generate an imaging beam and an optical cable to deliver the imaging beam towards an imaging probe. The imaging probe can be inserted into the eye to be positioned close to the target point, such as to a point of the retina. In some embodiments, the imaging probe can even be brought into contact with the retina, or at least positioned in close proximity to the retina. The target point may be a spot on the retina where the surgeon is plans to perform an ophthalmic surgical procedure. The imaging probe can project or focus an imaging beam onto the target point and then receive a returned of reflected beam, reflected from a range of depths corresponding to the target point.

0035The returned imaging beam can be delivered back to a detector of the OCT imaging system, where it can be interfered with a reference beam by a beam splitter to generate an interference beam. Processing the interference beam by the detector decodes image data related to the range of depths corresponding to the target point, all of it coded in the phase of the returned imaging beam. This processing can be performed by a scanning processor of the axial scanner, such as a scanning processor of the OCT imaging system.

0036In some embodiments, the image data can be not only a reflection strength, but also a scattering amplitude, an absorptivity, a noise, a fluctuation, and an optical data, corresponding to the range of depth of the target tissue. <figref idref="DRAWINGS">FIG. 5</figref> illustrates an example of imaging data: in this embodiment the imaging data is a relative reflection strength, measured in a range of depths of about 1.6 mm. This embodiment of the OCT imaging system has a high resolution, and thus measures the relative reflection strength at a very large number of depths within the depth range. OCT imaging systems can have a resolution of a few microns, thus in a depth range of a millimeter, they can determine the reflection strength at several hundreds or even at a thousand depths or depth points. Such a depth-scan, or axial scan, is often called an A-scan. In embodiments, the measuring image data can be performed without using fluorescent markers.

0037Step <b>320</b> can involve transferring the image data from the axial scanner to the imaging processor. In some embodiments, this can involve transferring the set of numerical values of the reflectivity at the large number of depths corresponding to the target point on the retina, such as the image data in <figref idref="DRAWINGS">FIG. 5</figref>. In some embodiments, this imaging processor can be different from the scanning processor of the axial scanner, as described in relation to <figref idref="DRAWINGS">FIG. 6</figref> below. In other designs, the functions of the scanning processor and the imaging processor can be performed by the same processor of a computer. In such designs, step <b>320</b> need not involve a transferring operation.

0038Step <b>320</b> can include determining image information by the imaging processor from the image data. The determining of image information can include identifying two or more image features, wherein an image feature can be one of a peak, valley, maximum, minimum, halfway point, transition point, and plateau of the image data as a function of depth.

0039In the example of <figref idref="DRAWINGS">FIG. 5</figref>, the imaging processor can use a search algorithm to determine local maxima of the relative reflection strength. For some retinal layers, detailed in relation to <figref idref="DRAWINGS">FIG. 1</figref>, their interfaces and boundaries scatter and reflect light stronger than their internal portions, the depth, or location of these layer-boundaries can be identified by identifying the local maxima of the reflectivity. In the case of some retinal layers, the entire layer can scatter or reflect the imaging light stronger than its neighboring layers. These layers can cause not only a local maximum, but a plateau, or sustained enhanced region in the image data, such as the reflectivity.

0040<figref idref="DRAWINGS">FIG. 5</figref> illustrates that the boundaries of retina <b>110</b> can be identified as local maxima of the relative reflection strength, located at depths of about 0.6 mm (600 microns) and at about 0.85 mm (850 microns). In the proximal region of retina <b>110</b>, NFL <b>112</b> can be identified from the elevated reflectivities, and in the distal region of retina <b>110</b>, RPE <b>113</b> can be identified from the elevated levels of the reflectivity.

0041Given the noisy nature of the image data, identifying the image features, such as maxima, minima, or plateaus can involve using mathematical techniques, such as an averaging, a smoothing, a linear regression technique, a spectral decomposition technique, a low-pass filter, a fitting procedure, or equivalents.

0042Step <b>320</b> can include determining not only the existence of image features, but also recording their depths. This can be followed by measuring or determining a depth difference between two of the identified image features. This depth difference can be part of the image information. The depth difference between the two outer surfaces of retina <b>110</b> is a measure of the thickness of retina <b>110</b>. In the example of <figref idref="DRAWINGS">FIG. 5</figref>, this depth difference d can be measured to be about d=0.85 mm−0.6 mm=0.25 mm (250 microns), as discussed below in more detail.

0043Since this process involves comparing the depths of different image features, the imaging processor can perform step <b>320</b> in conjunction with an imaging memory circuit, where some of the image data and the corresponding depths are stored.

0044Step <b>330</b> can include identifying a tissue pathology or anomaly that can involve determining an existence of the tissue pathology or determining a thickness of the tissue pathology based on the image information, or both. The tissue pathology or anomaly can be determined from the image information that includes the depth difference of image features and thus the information about the thickness of target layers, such as a retinal layer or the entire retina. In other embodiments, the tissue pathology or anomaly can be determined from the anomalous depths of the ophthalmic layers.

0045As discussed in relation to <figref idref="DRAWINGS">FIG. 1</figref>, several retinal diseases are accompanied by an anomalously increased retinal thickness. To recognize such retinal pathologies, the imaging processor can use the determined retinal thickness and perform a comparison to other relevant thicknesses. For example, the operation of the axial scanner can involve moving the scanning probe along a scanning line, recording the retinal thicknesses along the line in a memory circuit, comparing the thicknesses along the line by the imaging processor, and signaling if the thickness at a particular location or in a particular segment of the line is thicker or thinner than at others. Such a thickness anomaly can indicate a retinal disease.

0046Other retinal diseases or pathologies can be recognized from the retina's distal boundary surface exhibiting a depth different from the depth of proximal surface of the underlying supporting layer choroid <b>115</b>, signaling a retinal detachment. In yet other retinal diseases, the average retinal thickness may not be that different form a typical value, but the thickness may exhibit larger than usual spatial variations, indicating an anomalous unevenness of the retina. These are examples that the image information can be other than only a layer thickness.

0047<figref idref="DRAWINGS">FIG. 5</figref> illustrates the steps <b>310</b>, <b>320</b> and <b>330</b> in more detail. <figref idref="DRAWINGS">FIG. 5</figref> shows a partial view of A-scan <b>500</b> from retina <b>110</b>, according to some embodiments of method <b>300</b>. Scan <b>500</b> corresponds to the section labeled AA′ in <figref idref="DRAWINGS">FIG. 4</figref>, located at a lateral position of approximately 0.6 mm. Scan <b>500</b> displays the result of step <b>310</b>, the measurement of image data, in this case that of the relative reflectivity strength at a large number of depths within a depth segment 0-1.6 mm of the eye along an axial or Z-direction. The vitreous cavity <b>140</b> and the choroid <b>115</b> reflect only to a limited degree and therefore appear as regions with reduced reflectivity in scan <b>500</b>. Two peaks appear in the image data, corresponding to NFL <b>112</b> and RPE <b>113</b>. The space between a proximal surface of NFL <b>112</b> and a distal surface of RPE <b>113</b> is retina <b>110</b>, with thickness <b>510</b>.

0048In step <b>320</b>, the image features can be located by the imaging processor by performing an algorithm that searches the local maxima or other image features of the image data. Examples of the algorithm can include an averaging, a smoothing, a linear regression technique, a spectral decomposition technique, a low-pass filter, a fitting procedure, or equivalents.

0049In <figref idref="DRAWINGS">FIG. 5</figref> the image features include the two peaks and the corresponding depths. Thus, the imaging processor can determine the location of the proximal and the distal boundary surfaces of retina <b>110</b>. Still within step <b>320</b>, in some embodiments, the imaging processor can determine a depth difference of two image features, such as a depth difference of the two boundary surfaces. This difference is a reliable measure of the thickness <b>510</b> of retina <b>110</b>.

0050The knowledge of the location of the retinal boundaries and the retinal thickness allows in step <b>330</b> the imaging processor to determine the status of retinal tissue <b>110</b> at point A and to identify whether the retinal tissue exhibits a pathology or anomaly. Several tissue pathologies and the corresponding embodiments of step <b>330</b> will be discussed next.

0051For example, in certain conditions such as in the macular puckering <b>204</b> of <figref idref="DRAWINGS">FIG. 2</figref>, thickness <b>510</b> may be larger than a certain standard or threshold. Thus, in step <b>330</b> the determination of the image information that the retinal thickness exceeds a normal value, or is outside a normal range, can be interpreted as evidence for macular puckering. In other situations, enhanced thickness <b>510</b> may indicate an inflammation of retina <b>110</b> at point A.

0052In the case of retinal detachment such as <b>201</b>-<b>203</b> in <figref idref="DRAWINGS">FIG. 2</figref>, the image information gleaned from A-scan <b>500</b> may show excess materials <b>221</b>-<b>223</b> being present under detached retina <b>211</b>-<b>213</b>. Because blood and fluids in excess materials <b>221</b>-<b>223</b> may have a different reflectivity than choroid <b>115</b>, excess materials <b>221</b>-<b>223</b> may have a different reflectivity level in A-scan <b>500</b> than the valleys of vitreous gel <b>145</b> and choroid <b>115</b>.

0053In the macular puckering <b>204</b> of <figref idref="DRAWINGS">FIG. 2</figref>, a collection of A-scans taken at points of interest relatively close to one another may show a thickness <b>510</b> of retina <b>110</b> changing drastically between different points: another type of indication of a tissue pathology.

0054Yet another type of tissue pathology is connected to the posterior vitreous detachment <b>205</b> of <figref idref="DRAWINGS">FIG. 2</figref>. An A-scan <b>500</b> may provide indication of the presence of ILM <b>111</b>, epiretinal membrane <b>214</b>, and detached vitreous cortex <b>215</b>. Additionally, anomalous tissue <b>216</b> can also be present that can be either a fully detached portion of the retina, or in some cases, vitreous gel <b>145</b>.

0055In all of these embodiments, image data in A-scan <b>500</b> can exhibit image features, such as local maxima, elevated plateaus, sharp minima or valleys. The imaging processor can be configured to identify any and all of these image features and the corresponding depth values. Finally, the imaging processor can extract additional characteristics, such as the depth-difference or distance of image features that can be indicative of tissue thicknesses, or tissue detachments. The identification of the image features, their depths and the depth differences together can be part of the image information, determined by the imaging processor in step <b>320</b>. Based on these image information, in step <b>330</b> tissue pathologies can be determined, by the imaging processor. The imaging processor can evaluate tissue pathologies based on communicating with a lookup table that stores the correlation between image information and the various retinal pathologies.

0056Of the above-discussed embodiments, many involved measuring and analyzing a single A-scan. However, the efficiency of method <b>330</b> to recognize tissue pathologies can be enhanced by comparing the depth of the target tissue at a particular surface point to the depths at other surface points of the target tissue. To improve the efficiency by such multiple imaging procedures, method <b>300</b> can involve scanning the probe along a scanning line over the target region and performing A-scans at a set of points along the scanning line. A set of image data, corresponding to the sequence of target points, can be assembled by the scanning processor.

0057<figref idref="DRAWINGS">FIG. 4</figref> illustrates such an assembly of A-scans, typically referred to as a B-scan. In the B-scan shown, the reflectivity is indicated by a grey scale. For example, a sharp variation of the grey scale in a B-scan can indicate the tissue boundary. It is noted here that the terms “A-scan” and the “scanning of a depth segment” refer to gathering image data along a Z-axis of the imaging system at a fixed target point on the tissue surface. On the other hand, scanning in the context of the B-scan refers to a lateral scan of the probe and imaging beam, scanning the target point itself along the tissue surface, as the context makes it clear.

0058Once the imaging system creates a B-scan, the imaging processor can identify the image information and based on that, the tissue pathology by comparing the image information along the sequence of target points. Analogously to the A-scans, the imaging processor can use various mathematical techniques for this analysis, including averaging image information along the sequence of target points, filtering image information along the sequence of target points with a Kalman filter, using a linear regression technique, using a principal components analysis technique, and using a lookup table correlating at least one image information to at least one tissue pathology or tissue structure. Since the imaging processor is comparing image data and image information from sequentially taken A-scans, the imaging processor or the imaging system can include a memory circuit that can store the image data and image information of A-scans.

0059<figref idref="DRAWINGS">FIG. 4</figref> shows a partial view of B-scan <b>400</b>, generated by assembling a large number of A-scans, taken by an OCT technique on a healthy retina <b>110</b>, according to some embodiments. <figref idref="DRAWINGS">FIG. 4</figref> corresponds to a sagittal view of retinal tissue. B-scan <b>400</b> shows retina <b>110</b>, vitreous cavity <b>140</b>, and choroid <b>115</b>. A multilayered structure of retina <b>110</b> is evident in B-scan <b>400</b>. The upper or proximal layer includes NFL <b>112</b>, and the lower or distal layer includes RPE <b>113</b>. While other structures may be apparent in B-scan <b>400</b>, NFL <b>112</b> and RPE <b>113</b> are easily distinguishable because they provide the highest reflectivity in retina <b>110</b>. In fact, NFL <b>112</b> and RPE <b>113</b> provide the highest reflectivity in the entire field shown in B-scan <b>400</b>. This high reflectivity was shown also in the elevated values of reflectivity in <figref idref="DRAWINGS">FIG. 5</figref>.

0060In embodiments of the method <b>300</b> the probe of the axial scanner, such as the OCT imaging scanner, can be inserted into the eye before measuring image data. This feature, the insertable probe, can force requirements on the imaging system that are considerably more stringent than the requirements of ophthalmic imaging systems that are used only externally. Probes can be inserted only in a surgical environment, whereas external probes can be operated in an outpatient office, such as in a diagnostic environment.

0061The signaling in step <b>340</b> can include providing a visual or non-visual signal to the user of the system, such as the surgeon. The user indicator may provide a blinking of a light beam aimed at the target point on the retina to signal the tissue pathology or structure. Thus, in step <b>340</b> the user indicator may indicate the tissue pathology determined in step <b>330</b> by projecting a visual signal on the retina itself. For example, blinking once may indicate the presence of only ILM <b>111</b> (healthy retina). Blinking twice may indicate the presence of epiretinal membrane or puckering <b>214</b>, and blinking three times may indicate the presence of detached vitreous cortex <b>215</b>. Providing these signals without forcing the surgeon to look away from the surgical microscope makes the job of the surgeon much easier: the surgeon can concentrate on performing the scanning imaging of the target tissue with the probe and will not be forced to repeatedly turn away from the surgical microscope and analyze complex images for pathologies.

0062In other embodiments, the imaging system can display a heads-up signal in the surgical microscope. In yet other embodiments, the blinking of an aiming or sensing optical beam may be replaced or complemented by an audible beep. A single beep may indicate ILM <b>111</b> only, two beeps may indicate membrane <b>214</b>, and three beeps may indicate detached cortex <b>215</b>. Other embodiments consistent with <figref idref="DRAWINGS">FIGS. 3-5</figref> may include the use of other non-imaging or non-optical indicators for the tissue structure or pathology. These embodiments, a surgeon is made aware of whether there is ILM <b>111</b>, epiretinal membrane <b>214</b>, or detached vitreous cortex <b>215</b> without the need to interpret a complex image.

0063Some embodiments of the methods, procedures and apparatus disclosed herein may include the removal of waste material from retinal layers such as RPE <b>113</b>. Waste materials such as lipofuscin tend to be highly toxic, and photosensitive. Thus, photocoagulation techniques as described above may be used to remove such materials, according to methods consistent with <figref idref="DRAWINGS">FIGS. 3-5</figref>. For example, an OCT A-scan <b>500</b> may be used to determine the presence of lipofuscin material at a target point. In step <b>340</b>, a signal from an user indicator can prompt either a surgeon or an automatic mechanism to make an operational decision, such as providing a certain dosage of light to the target point.

0064In this example, if the lipofuscin is not present or is present at a level below a certain threshold, a new point of interest may then be selected. Analogously, in most embodiments, if no tissue pathology has been detected in steps <b>310</b>-<b>330</b>, then the user indicator can provide a signal for the surgeon or for an automated controller to move the scanning probe to a new point.

0065<figref idref="DRAWINGS">FIG. 6</figref> shows an embodiment of an imaging system <b>600</b> to detect a tissue pathology or anomaly in ophthalmic surgery according to some embodiments. According to <figref idref="DRAWINGS">FIG. 6</figref>, imaging system <b>600</b> may be configured to determine an ophthalmic tissue pathology or anomaly and may include an axial scanner <b>610</b> with a probe <b>611</b> to measure image data for a range of depths corresponding to a target point P <b>601</b> in an eye. Imaging system <b>600</b> may further include an imaging computer <b>620</b> with an imaging processor <b>622</b> to determine an image information from the image data and to identify a tissue pathology corresponding to the target point P <b>601</b> from the image information; and a user indicator <b>630</b> to signal a user based on the identified tissue pathology. Some embodiments can also include surgical console <b>640</b>.

0066Scanner <b>610</b> can include imaging probe <b>611</b>, scanning processor <b>612</b>, and memory circuit <b>613</b>. In some embodiments of system <b>600</b>, probe <b>611</b> is an optical probe providing a beam of light directed to P <b>601</b> through a line of sight (LOS). LOS is shown as a dashed line from distal portion <b>611</b><i>p </i>of probe <b>611</b> to target point P <b>601</b>. The optical cable and distal portion <b>611</b><i>p </i>of probe <b>611</b> can guide an imaging light from scanner <b>610</b> to the target point P <b>601</b>. Distal portion <b>611</b><i>p </i>also receives the returned imaging light, reflected by the tissue at the target point P <b>601</b>. Probe <b>611</b> carries back the returned imaging light a signal providing image data from P <b>601</b>. In some embodiments, portion <b>611</b><i>p </i>may be inserted inside eye <b>100</b>. In other embodiments, probe <b>611</b> may provide illumination light through the cornea, without being inserted into the eye.

0067The returned imaging beam from probe <b>611</b> can be analyzed by scanning processor <b>612</b> and stored in memory circuit <b>613</b>. Memory circuit <b>613</b> may also store image data corresponding to target points the probe portion <b>611</b><i>p </i>was directed at before it was directed to P <b>601</b>. As before, the image data can include the reflectivity of the target tissue in a range of depth and the corresponding depth values. The image data can also include the lateral position of the imaging probe's distal portion <b>611</b><i>p</i>, as it was shown in <figref idref="DRAWINGS">FIG. 4</figref>. Scanning processor <b>612</b> may perform operations on the image data extracted from returned imaging beam, such as noise filtering, averaging, and calibrating with a reference value.

0068The length of portion <b>611</b><i>p </i>may be 3-4 inches (approximately 7.5 cm to 10 cm), or more. Portion <b>611</b><i>p </i>may have a broader part or hand-piece to be handled by a surgeon, and a tip or narrow end in its distal portion. The broad part or hand-piece in portion <b>611</b><i>p </i>may be about 8 mm to about 18 mm in diameter, and between 45 mm and 90 mm in length. In some embodiments the tip may be approximately 25 to 35 mm in length and have a diameter between 20 gauge and 25 gauge, or less than about 1 mm to about 0.5 mm. Some embodiments of probe <b>611</b> may include portion <b>611</b><i>p </i>being smaller than 25 gauge, such as 27 gauge or even smaller. In some embodiments the diameter of portion <b>611</b><i>p </i>may be as low as 50 gauge. Probe <b>611</b><i>p </i>may be an endoprobe in which the distal end is inserted into the eye <b>100</b>, according to some embodiments. In other embodiments, probe <b>611</b><i>p </i>may be outside the eye <b>100</b>, illuminating point P <b>601</b> through the cornea.

0069Scanner <b>610</b> can be coupled to imaging computer <b>620</b> and provide imaging computer <b>620</b> the image data generated by scanning processor <b>612</b>. Imaging computer <b>620</b> can include imaging processor <b>622</b> and memory circuit <b>623</b>. According to some embodiments of system <b>600</b>, imaging computer <b>620</b> and scanner <b>610</b> may be integrated into a single unit. In such cases, scanning processor <b>612</b> and imaging processor <b>622</b> may be the same processor circuit, or different portions of the same processor circuit. Also, memory circuits <b>613</b> and <b>623</b> may be the same circuit, or different portions of the same memory circuit. Memory circuit <b>623</b> may store information regarding a set of points P <b>601</b>, and imaging processor <b>622</b> may perform calculations using this information.

0070In some embodiment of system <b>600</b> the imaging processor <b>622</b> can identify two or more image features, wherein an image feature is one of a peak, valley, maximum, minimum, halfway point, transition point, and plateau of the image data as a function of depth; and measure a depth difference between two of the identified image features, wherein the depth difference is part of the image information.

0071The imaging processor <b>622</b> can be able to identify the tissue pathology by averaging image information along the sequence of target points, filtering image information along the sequence of target points with a Kalman filter, using a linear regression technique, using a principal components analysis technique or using a lookup table correlating at least one image information to at least one tissue structure.

0072For example, imaging processor <b>622</b> may perform data smoothing operations in order to remove transient fluctuations in the signal. In some embodiments, such smoothing operations may include averaging signals produced by the set of points P <b>601</b>. Other embodiments may include the use of frequency filters and windows for data processing in imaging processor <b>622</b>. Further embodiments may include the use of a Kalman filter having a predictor value and a standard deviation from the predictor value.

0073Based on a determination of tissue pathology or structure at P <b>601</b> in step <b>330</b>, imaging computer <b>620</b> can provide a signal to user indicator <b>630</b>. User indicator <b>630</b> can communicate the tissue pathology information to the surgeon or technician performing the surgical intervention. User indicator <b>630</b> may be a laser or light source providing visible light through the optical path of probe <b>611</b> to illuminate the target point with light having a certain color. As mentioned above the visible light of indicator <b>630</b> may include a light beam having a visible color, such as red, green, or blue. Thus, once an image information is used by imaging processor <b>622</b> to determine a tissue pathology, imaging computer <b>620</b> can signal user indicator <b>630</b> to use a light source having a pre-selected color and provide an indicator beam through the optical path of probe <b>611</b> to indicate for the user of the imaging system <b>600</b> the determined tissue pathology or anomaly. As discussed above, the indication can be a visual or non-visual signal, and can be such that it does not force the surgeon to look away from the surgical microscope.

0074Some embodiments of system. <b>600</b> may further include a surgical microscope providing a view of the target point P <b>601</b> during the intervention. In these embodiments, the user indicator <b>630</b> may be a visual indicator as described above, coupled to the distal end of probe <b>611</b><i>p</i>. In such embodiments, the signal provided by the user indicator <b>630</b> may be projected onto the target tissue and into the view of the surgical microscope.

0075According to embodiments of system <b>600</b>, imaging computer <b>620</b> may be coupled to a surgical console <b>640</b>, and can provide the tissue pathology determination to surgical console <b>640</b>. Surgical console <b>640</b> can include mechanical devices and systems to perform the ophthalmic surgical intervention on eye <b>100</b>. Some embodiments may include surgical actuator <b>641</b> having a tip in the distal end, to perform the intervention. For example, actuator <b>641</b> may include a pair of scissors at the distal end. Other uses, procedures, and components of surgical console <b>640</b> to perform ophthalmic surgery may be evident to one of regular skill in the art. Corresponding ophthalmic surgical components can be included herein in embodiments of system <b>600</b> consistent with the concept illustrated in <figref idref="DRAWINGS">FIG. 6</figref>.

0076In some embodiments of system <b>600</b> as illustrated in <figref idref="DRAWINGS">FIG. 6</figref>, the tissue structure or pathology determination provided by imaging computer <b>620</b> may be used by surgical console <b>640</b>. Surgical console <b>640</b> may update its configuration status based on the tissue anomaly determination at P <b>601</b>. For example, if it is determined that the structure at P <b>601</b> corresponds to one of the pathologies <b>201</b>-<b>205</b> of <figref idref="DRAWINGS">FIG. 2</figref>, then console <b>640</b> may enable surgical actuator <b>641</b> and prepare the tip for an intervention. This may include powering up the teed mechanism for a pair of scissors, such as a pneumatic scissor system. Thus, while the ultimate command can still be provided by the surgeon, system <b>600</b> may get console <b>640</b> ready to perform the intervention. Embodiments of system <b>600</b> using this approach can provide a smooth and quick pace for ophthalmic surgery, enabling the surgeon to concentrate on the intervention itself. Also, embodiments of system <b>600</b> can provide the surgeon with extra time prior to performing the intervention at each point P <b>601</b>, review the procedure, and think ahead of the next surgical steps.

0077In some embodiments consistent with <figref idref="DRAWINGS">FIGS. 3-6</figref>, collecting a B-scan from a plurality of A-scans may include the use of a gyroscope and an accelerometer to track the trajectory of axial scanner with a probe <b>610</b> (such as an OCT scanner) along different points of interest <b>601</b>. Other means for tracking axial scanner <b>610</b> with a probe <b>611</b> may include the use of a magnetic sensor to track the motion of probe portion <b>611</b><i>p</i>. In some embodiments, a gyroscope, an accelerometer, and a magnetic sensor may be included in axial scanner with a probe <b>610</b>, having a sensor coupled to portion <b>611</b><i>p</i>. In some embodiments, a gyroscope, an accelerometer, and a magnetic sensor may be controlled automatically from surgical console <b>640</b>. Some embodiments may use a surgical microscope as described above for tracking the motion of probe portion <b>611</b><i>p </i>from one point <b>601</b> to the next. The surgical microscope may provide a digital image to a processor such as <b>612</b> or <b>622</b>, or to a controller included in console <b>640</b>. The digital image may be processed to determine precisely the location of target point P <b>601</b> within eye <b>100</b>. Thus, a B-scan may be formed from a collection of precisely tracked A-scans.

0078More generally, the tracking methods and devices described above (e.g., gyroscope, accelerometer, and magnetic sensors) may be used to track the movement of probe portion <b>611</b><i>p </i>along a trajectory in a plane substantially perpendicular to the axial scan. In some embodiments, the motion of probe portion <b>611</b><i>p </i>along such a trajectory may be complemented with the motion of an optical beam coming out of probe portion <b>611</b><i>p</i>. For example, an optical beam forming the LOS depicted by a dashed line in <figref idref="DRAWINGS">FIG. 6</figref> may describe a trajectory for point <b>601</b> in a plane substantially perpendicular to the axial scan, or to the axis of portion <b>611</b><i>p</i>, according to some embodiments.

0079Embodiments of the invention described above are exemplary only. One skilled in the art may recognize various alternative embodiments from those specifically disclosed. Those alternative embodiments are also intended to be within the scope of this disclosure. As such, the invention is limited only by the following claims.